Oximeter probe off indicator defining probe off space

ABSTRACT

An embodiment of the present disclosure seeks to select characteristics of incoming intensity data that cause comparisons of selected characteristics to produce defined probe off space having reduced crossover with defined probe on space. Once defined, the present disclosure compares characteristics of incoming intensity data with the now defined probe off space, and in some embodiments, defined probe on space, to determine whether a probe off condition exists. When a processor determines a probe off condition exists, the processor may output or trigger an output signal that audibly and/or visually indicates to a user that the optical sensor should be adjusted for a proper application to a measurement site.

PRIORITY CLAIM

This present application claims priority benefit under 35 U.S.C. §119(e)from U.S. Provisional Application No. 60/851,448, filed Oct. 12, 2006,entitled “Oximeter Probe Off Indicator Defining Probe Off Space,” whichis incorporated by reference herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is related to U.S. Pat. Nos. 6,526,300,6,654,624, and the continuation, continuation-in-part, and divisionalapplications thereof. The foregoing disclosures are incorporated hereinby reference and included in the present provisional filing.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates in general to patient monitoring and inparticular to oximeter patient monitors capable of indicating probe offconditions.

2. Description of the Related Art

Oximeter systems providing measurements of a monitored patient havebecome the standard of care in many patient care settings, includingsurgical, post surgical, neonatal, general ward, home care, physicaltraining, and the like. In general, oximeter systems accept one or morenoninvasive signals from an optical sensor or probe capable of emittinglight into a tissue site and capable of detecting light attenuated bythe tissue site. Accurate determination of the measurements andaudio/visual indications is often dependent upon proper application ofthe optical sensor to the tissue site. In the present disclosure, “probeon” conditions include their ordinary broad meaning known to one ofskill in the art, including designating proper application of an opticalprobe to a measurement site. “Probe off” conditions include theirordinary broad meaning known to one of skill in the art, includingdesignating improper application of an optical probe to a measurementsite.

Many oximeters may fail to accurately detect probe off conditions. Asstated, this condition occurs when the optical sensor becomes partiallyor completely dislodged from the patient (measurement site), butcontinues to detect signals. Probe off errors can be serious because theoximeter may output normal measurements, and audio/visual indications ofthe monitored parameters when, in fact, the probe is not properlyattached to the patient, probe off errors may potentially lead to missedphysiological events.

Several solutions to more accurately monitor and detect probe offconditions are disclosed in U.S. Pat. No. 6,654,624, assigned to MasimoCorporation (“Masimo”) of Irvine, Calif., and incorporated by referenceherein. For example, the '624 patent discloses monitor-based detectionof probe off conditions. In particular, an intelligent, rule-basedprocessor uses signal quality measurements to limit the operating regionof the oximeter without significant negative impact on low perfusionperformance. These signal-quality operating limits are superimposed on agraph of signal strength versus emitter gain to improve probe offdetection. In this manner, the oximeter can reject intensity signalsthat have sufficient signal strength to fall within an operating region,but that are unlikely to be a plethysmograph signal. One signal qualitymeasurement that is used is pulse rate density, which is the percentageof time detected pulses satisfy a physiologically acceptable model.Another signal quality measurement is harmonic energy ratio, which isthe percentage of signal energy that occurs at the pulse rate and itsharmonics. The operating region of the oximeter is then defined in termsof signal strength versus gain, signal strength versus PR density andenergy ratio versus predefined energy ratio limits. Thus, the '624disclosure seeks to limit the scope of acceptable probe on space, asdefined by signal strength versus gain, PR density, and energy ratios,and seeks to designate all non-probe on space as probe off space.

SUMMARY OF THE DISCLOSURE

An embodiment of the present disclosure seeks to select characteristicsof incoming intensity data that cause comparisons of the selectedcharacteristics to produce defined probe off space having reducedcrossover with defined probe on space. Once defined, the presentdisclosure compares characteristics of incoming intensity data with thenow defined probe off space, and in some embodiments, probe on space, todetermine whether a probe off condition exists. When a processordetermines a probe off condition exists, the processor may output ortrigger an output signal that audibly and/or visually indicates to auser that the optical sensor should be adjusted for a proper applicationto a measurement site.

In an embodiment, the characteristics include ratio data, such as, forexample, data of signals responsive to the intensity signals normalizedthrough division by one of the intensity signals. Such divisiongenerates ratio data channels, each indicative of one intensity signalother than the normalizing signal. The ratio data channels can bemonitored during clinical or other trials where probe off conditions areknown to exist. Moreover, oximeter manufacturers typically monitor ratiodata channels during, for example, the clinical trials to relateacquired data to the accurate determination of physiological parametermeasurements and/or the audio and visual indications of the same. Thus,probe off trial data can be usable to determine probe off space definedin the context of the acquired ratio data on two or more data channels.Moreover, the clinical trial data can also be usable to determine probeon space defined in the context of the acquired ratio data on one ormore of the ratio data channels during valid patient monitoring.

Once the probe off space, and in some embodiments, the probe on space,is defined, ratio data acquired before, periodically during, randomly orpseudo-randomly during patient measurements, combinations of the same,or the like, can be compared against stored probe off and probe onspaces to determine whether a probe off condition exists.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the disclosure have been described herein. Ofcourse, it is to be understood that not necessarily all such aspects,advantages or features will be embodied in any particular embodiment ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of thedisclosure will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the disclosure and not to limit its scope.

FIG. 1 illustrates an exemplary oximeter patient monitoring system,according to an embodiment of the disclosure.

FIG. 2 illustrates an exemplary block diagram of the oximeter patientmonitoring system of FIG. 1.

FIG. 3 illustrates exemplary tables of ratio channel data for probe onand probe off conditions, according to an embodiment of the disclosure.

FIGS. 4-7 illustrate exemplary comparative graphs of the ratio channeldata of FIG. 3.

FIG. 8 illustrates a simplified exemplary block diagram of a probe offdetector, according to an embodiment of the disclosure.

FIG. 9 illustrates an exemplary probe off determination method,according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To facilitate a further understanding of the disclosure, the remainderof the description describes the disclosure with reference to specificdrawings. Moreover, in this application, reference is made to bloodparameters. Some references have common shorthand designations. Forexample, as used herein, HbCO designates carboxyhemoglobin, HbMetdesignates methemoglobin, HbT designates total hemoglobin, SpO₂designates functional arterial saturation, and SpaO₂ designatesfractional arterial saturation. Other shorthand designations such asCOHb, MetHb, and tHb are also common in the art for these sameconstituents. These constituents are generally reported in terms of apercentage, often referred to as saturation, relative concentration,concentration, or fractional saturation. Total hemoglobin is generallyreported as a concentration in g/dL. The use of the particular shorthanddesignators presented in this application does not restrict the term toany particular manner in which the designated constituent is reported.

FIG. 1 illustrates a perspective view of a patient monitor system 100,according to an embodiment of the present disclosure. The system 100includes a portable patient monitor 102 capable of noninvasivelydetermining one or more physiological parameters. In an embodiment, theportable patient monitor 102 may mechanically and electrically mate witha docking station 104 to recharge batteries, upload and downloadinformation, upgrade software or firmware, communicate with othermonitors or the like. The monitor 102 also comprises one or moredisplays 106 capable displaying of a wide variety of measured values ina manner that provides for quick and efficient conveyance of informationto a caregiver. For example, the display 106 displays values for HbCO108, HbMet 109, MbT 110, SpO₂ 112, SpaO₂ 114, beats-per-minute 116,scaled plethysmograph data 118, PI™ 120 and other information includinginformation audibly and/or visually alerting a caregiver to any probeoff conditions. The other information may include historical or trendingdata, combined parameter data, confidence or perfusion indicators, orthe like.

FIG. 1 further illustrates the monitor 102 communicating with a reusableoptical sensor 154 through a patient cable 156. In general, the monitor102 drives the sensor 154 to emit light of differing wavelengths intothe body tissue 158. The sensor 154 detects the light after attenuationby the body tissue 158 and outputs a signal indicative of the amount oflight received by the sensor 154 through the cable 156. In addition, insome embodiments, the monitor 102 communicates with a temperature sensorand/or a memory device associated with one or more of the sensor 154 andthe cable 156.

In an embodiment, the monitor 102 receives sensor output and determinescontinuous and non-invasive measurements of a wide variety of bloodparameters. Although disclosed with reference to the portable monitors102, an artisan will recognize from the disclosure herein that aspectsof the present disclosure can be adopted into tabletop monitors,wireless sensors, or other patient-wearable personal monitors, ormulti-parameter patient monitors.

The sensor 154 may advantageously comprise a reusable sensor in the forma clip including a spring biased pivot point capable of removablyattaching the reusable sensor to a patient's finger 158. Althoughdisclosed with reference to a reusable sensor having a spring, anartisan will recognize from the disclosure herein that the sensor 154can advantageously comprise a disposable adhesive type sensor, acombination sensor including reusable and disposable components,components incorporated into other medical devices such as catheters, orthe like, or other reusable sensor designs. Moreover, the artisan willrecognize from the disclosure herein that the sensor 154 can comprisemechanical structures, adhesive or other tape structures, Velcro wrapsor combination structures specialized for the type of patient, type ofmonitoring, type of monitor, or the like. In an embodiment, the sensor154 provides data to the monitor 102, and vice versa through the cable156, although such communication can advantageously be wireless, overpublic or private networks or computing systems or devices, throughintermediate medical or other devices, combinations of the same, or thelike. In an embodiment, the monitor 102 may include one or more audio,visual or messaging (pagers, emails, instant and phone messages, vocallypresented numbers, messages and alarms, voice-over-IP (“VoIP”)interfaces and functionality, or the like) alarms, user input keypad160, or the like.

Although described in terms of certain embodiments, other embodiments orcombination of embodiments will be apparent to those of ordinary skillin the art from the disclosure herein. For example, the monitor 102 maycombine other information with intensity-derived information toinfluence diagnoses or device operation. For example, patterns orchanges in the continuous noninvasive monitoring of intensity-derivedinformation may cause the activation of other vital sign measurementdevices, such as, for example, blood pressure cuffs. Moreover, themonitor 102 may comprise a personal or wearable noninvasivemulti-parameter patient monitor that wirelessly communicates with amonitoring station to provide the monitoring station with measurementsfor some or all of the physiological parameters measurable by themonitor. For example, the monitor may travel with a patient as thepatient, for example, moves through a care site such as a hospital.Wireless networks incorporating such personal pulse technologies arecommercially available from Masimo marketed under the brand RadNet™ andRadLink™. Other monitors 102 may include a wireless patient monitorwhere a traditional sensor communicates with a wireless transmissiondevice wearable, for example, on the wrist. In other embodiments, thewireless transmission device may advantageously be incorporated into asensor housing adapted for wireless communication. In an embodiment, awireless receiver communicates with a sensor port in the same manner asa wired sensor. Thus, a traditional sensor and a traditional sensor portmay be unaware that a patient cable has been replaced with wirelesstransmissions.

FIG. 2 illustrates an exemplary block diagram of an embodiment of apatient monitoring system 200. As shown in FIG. 2, the system 200includes a patient monitor 202 comprising a processing board 204 and ahost instrument 208. The processing board 204 communicates with a sensor206 to receive one or more intensity signal(s) indicative of one or moreparameters of tissue of a patient. The processing board 204 alsocommunicates with a host instrument 208 to display determined parametervalues calculated using the one or more intensity signals. According toan embodiment, the board 204 comprises processing circuitry arranged onone or more printed circuit boards capable of installation into themonitor 202, or capable of being distributed as some or all of one ormore OEM components for a wide variety of host instruments monitoring awide variety of patient information. In an embodiment, the processingboard 204 comprises a sensor interface 210, a digital signal processorand signal extractor (“DSP” or “processor”) 212, and an instrumentmanager 214. In general, the sensor interface 210 converts digitalcontrol signals into analog drive signals capable of driving sensoremitters, and converts composite analog intensity signal(s) from lightsensitive detectors into digital data.

In an embodiment, the sensor interface 210 manages communication withexternal computing devices. For example, in an embodiment, amultipurpose sensor port (or input/output port) is capable of connectingto the sensor 206 or alternatively connecting to a computing device,such as a personal computer, a PDA, additional monitoring equipment ornetworks, or the like. When connected to the computing device, theprocessing board 204 may upload various stored data for, for example,off-line analysis and diagnosis. The stored data may comprise trend datafor any one or more of the measured parameter data, plethysmographwaveform data acoustic sound waveform, or the like. Moreover, theprocessing board 204 may advantageously download from the computingdevice various upgrades or executable programs, may perform diagnosis onthe hardware or software of the monitor 202. In addition, the processingboard 204 may advantageously be used to view and examine patient data,including raw data, at or away from a monitoring site, through datauploads/downloads, or network connections, combinations, or the like,such as for customer support purposes including software maintenance,customer technical support, and the like.

According to an embodiment, the DSP 212 comprises a processing devicebased on the Super Harvard ARChitecture (“SHARC”), such as thosecommercially available from Analog Devices. However, a skilled artisanwill recognize from the disclosure herein that the DSP 212 can comprisea wide variety of data and/or signal processors capable of executingprograms for determining physiological parameters from input data. Inparticular, the DSP 212 includes program instructions capable ofreceiving multiple channels of data related to one or more intensitysignals representative of the absorption (from transmissive orreflective sensor systems) of a plurality of wavelengths of emittedlight by body tissue. In an embodiment, the DSP 212 accepts data relatedto the absorption of two (2) to eight (8) wavelengths of light, althoughan artisan will recognize from the disclosure herein that the data canbe related to the absorption of two (2) to sixteen (16) or morewavelengths.

The processing board 204 also includes the instrument manager 214.According to an embodiment, the instrument manager 214 may comprise oneor more microcontrollers controlling system management, including, forexample, communications of calculated parameter data and the like to thehost instrument 208. The instrument manager 214 may also act as awatchdog circuit by, for example, monitoring the activity of the DSP 212and resetting it when appropriate.

The sensor 206 may comprise a reusable clip-type sensor, a disposableadhesive-type sensor, a combination sensor having reusable anddisposable components, or the like. Moreover, an artisan will recognizefrom the disclosure herein that the sensor 206 can also comprisemechanical structures, adhesive or other tape structures, Velcro wrapsor combination structures specialized for the type of patient, type ofmonitoring, type of monitor, or the like. In an embodiment, the sensor206 provides data to the board 204 and vice versa through, for example,a patient cable. An artisan will also recognize from the disclosureherein that such communication can be wireless, over public or privatenetworks or computing systems or devices, or the like.

The sensor 206 includes a plurality of emitters 216 irradiating the bodytissue 218 with differing wavelengths of light, and one or moredetectors 220 capable of detecting the light after attenuation by thetissue 218. The sensor 206 may also include other electrical componentssuch as, for example, a memory device 222 comprising an EPROM, EEPROM,ROM, RAM, microcontroller, combinations of the same, or the like. In anembodiment, other sensor components may include a temperaturedetermination device 223.

The memory 222 may advantageous store some or all of a wide variety dataand information, including, for example, information on the type oroperation of the sensor 206; type or identification of sensor buyer ordistributor or groups of buyer or distributors, sensor manufacturerinformation, sensor characteristics including the number of emittingdevices, the number of emission wavelengths, data relating to emissioncentroids, data relating to a change in emission characteristics basedon varying temperature, history of the sensor temperature, current, orvoltage, emitter specifications, emitter drive requirements,demodulation data, calculation mode data, the parameters for which thesensor is capable of supplying sufficient measurement data (e.g., HbCO,HbMet, HbT, or the like), calibration or parameter coefficient data,software such as scripts, executable code, or the like, sensorelectronic elements, whether the sensor is a disposable, reusable,multi-site, partially reusable, partially disposable sensor, whether itis an adhesive or non-adhesive sensor, whether the sensor is areflectance, transmittance, or transreflectance sensor, whether thesensor is a finger, hand, foot, forehead, or ear sensor, whether thesensor is a stereo sensor or a two-headed sensor, sensor life dataindicating whether some or all sensor components have expired and shouldbe replaced, encryption information, keys, indexes to keys or hashfunctions, or the like, monitor or algorithm upgrade instructions ordata, some or all of parameter equations, information about the patient,age, sex, medications, and other information that may be useful for theaccuracy or alarm settings and sensitivities, trend history, alarmhistory, or the like. In an embodiment, the monitor may advantageouslystore data on the memory device, including, for example, measuredtrending data for any number of parameters for any number of patients,or the like, sensor use or expiration calculations, sensor history, orthe like.

The patient monitor 202 also includes the host instrument 208. In anembodiment, the host instrument 208 communicates with the board 204 toreceive signals indicative of the physiological parameter informationcalculated by the DSP 212. The host instrument 208 preferably includesone or more display devices 224 capable of displaying indiciarepresentative of the calculated physiological parameters of the tissue218 at the measurement site. In an embodiment, the host instrument 208may advantageously comprise a handheld housing capable of displayingparameter data, including but not limited to pulse rate, plethysmographdata, perfusion quality such as a perfusion quality index (“PI™”) signalor measurement quality (“SIQ”), values of blood constituents in bodytissue, including for example, SpO₂, HbCO, HbMet, Hbt, or the like. Inother embodiments, the host instrument 208 is capable of displayingvalues for one or more of Hbt, Hb, blood glucose, bilirubin, or thelike. The host instrument 208 may be capable of storing or displayinghistorical or trending data related to one or more of the measuredvalues, combinations of the measured values, plethysmograph data, or thelike. The host instrument 208 also includes an audio indicator 226 anduser input device 228, such as, for example, a keypad, touch screen,pointing device, voice recognition device, or the like.

In still additional embodiments, the host instrument 208 includes audioor visual alarms that alert caregivers that one or more physiologicalparameters are falling below predetermined safe thresholds. The hostinstrument 208 may include indications of the confidence a caregivershould have in the displayed data. In a further embodiment, the hostinstrument 208 may advantageously include circuitry capable ofdetermining the expiration or overuse of components of the sensor 206,including, for example, reusable elements, disposable elements, orcombinations of the same.

Although described in terms of certain embodiments, other embodiments orcombination of embodiments will be apparent to those of ordinary skillin the art from the disclosure herein. For example, the monitor 202 maycomprise one or more monitoring systems monitoring parameters, such as,for example, vital signs, blood pressure, ECG or EKG, respiration,glucose, bilirubin, or the like. Such systems may combine otherinformation with intensity-derived information to influence diagnosis ordevice operation. Moreover, the monitor 202 may advantageously includean audio system, preferably comprising a high quality audio processorand high quality speakers to provide for voiced alarms, messaging, orthe like. In an embodiment, the monitor 202 may advantageously includean audio out jack, conventional audio jacks, headphone jacks, or thelike, such that any of the display information disclosed herein may beaudiblized for a listener. For example, the monitor 202 may include anaudible transducer input (such as a microphone, piezoelectric sensor, orthe like) for collecting one or more of heart sounds, lung sounds,trachea sounds, or other body sounds and such sounds may be reproducedthrough the audio system and output from the monitor 202. Also, wired orwireless communications (such as Bluetooth or WiFi, including IEEE801.11a, b, or g), mobile communications, combinations of the same, orthe like, may be used to transmit the audio output to other audiotransducers separate from the monitor 202. In addition, patterns orchanges in the continuous noninvasive monitoring of intensity-derivedinformation may cause the activation of other vital sign measurementdevices, such as, for example, blood pressure cuffs.

FIG. 2 also illustrates the DSP 112 including memory capable of storingdata indicative of a defined probe off space 260 and a defined probe onspace 262. In a further embodiment, the spaces 260, 262 include ratiodata 264, 266. For example, the probe off space 260 or probe on space262 may include data acquired through clinical or other trials wheredata was gathered during known probe off conditions. Examples of suchtrials may include a myriad of possible common occurrences in hospitalor caregiver settings, such as, for example, attaching a reusable clipto a standard hospital bed sheet, instrument pole, clothing, or leavingthe clip hanging in the air in one or a variety of lighting conditions.In addition, in an embodiment, the probe off data 260 may includeclinical experiments where a sensor hangs approximately eighteen (18)inches off the edge of a desk with a fan set on low placed about three(3) feet from the sensor. Data was collected in five-minute intervals invarious lighting conditions, including, for example: (1) ambient light,such as when lights are on in a room; (2) dim or dark light, such aswhen many of the lights are off in the room; (3) shadow light, such aswhen lights are off and a separate light is positioned to create shadowsfrom the desk edge that the sensor will swing in to and out of duringdata collection; (4) reflective light, such as when a box is placedapproximately six (6) inches from the sensor with the sensor lightemitters facing the box, and (i) all lights are on in the room, and (ii)all other lights are off in the room.

While disclosed with reference to some or all of the foregoing clinicaldata collections, an artisan will recognize from the disclosure hereinthat many common probe off environmental conditions could be simulatedto create large data sets of ratio channel data during such probe offconditions, including, for example, collection of data when emitters anddetector are separated only by air, or the like.

The probe on space 262 may include data acquired through clinical orother trials where data was gathered to, for example, determinecorrelations between monitor acquired measurement data and clinically ormodel acquired measurement data. Such experiments carefully monitor thecondition of probe placement, and therefore, generally define probe onspace. Such probe on space may be further limited using techniquesdisclosed, for example, in the '624 patent referenced in the foregoingor other techniques recognizable to an artisan from the disclosureherein.

FIG. 3 illustrates exemplary tables 302, 304 of ratio data for probe on304 and probe off 302 conditions, according to an embodiment of thedisclosure. As shown in FIG. 3, the probe off table 302 comprises ratiodata ranges for data channels associated with particular wavelengths inat least an eight (8) wavelength oximeter system, the ratio data rangesacquired, for example, during one or more of the foregoing probe offclinical trials. For example, in an embodiment, the monitor drives eight(8) light-emitting diodes (LEDs) with nominal centroids at about 610,about 620, about 630, about 660, about 700, about 730, about 800 andabout 905 nm. Although disclosed in reference to certain preferredwavelengths, an embodiment of the eight (8) emission centroids may rangefrom about 605 nm to about 614 nm, from about 615 nm to about 624 nm,from about 625 nm to about 635 nm, from about 655 nm to about 665 nm,from about 690 nm to about 710 nm, from about 720 nm to about 740 nm,from about 785 nm to about 825 nm, and from 875 nm to about 935 nm. Anartisan will recognize from the disclosure herein that other wavelengthsmay be of particular value based on, for example, the absorption spectraof desired physiological parameters, their responsiveness to probe offconditions, or the like. For example, experimental data may determinethat wavelengths different from those particularly useful in determiningmeasurement and other displayed data may advantageously be used todetermine probe off and/or probe on conditions, as discussed herein. Aparticular patient monitor may use a certain number of wavelengths formeasurement channels and some subgroup or an entirely differentadditional group of wavelengths for the probe off determinations. Forexample a monitor may use two (2) to eight (8) or more wavelengthsselected for their responsiveness to physiological parameters, and mayuse one (1) to eight (8) or more overlapping, entirely different, or thelike, of wavelengths for probe off and/or probe on determinations. Insuch embodiments, the wavelengths may be determined based on theirability to clearly distinguish probe off space from probe on space.

The data channel 306 corresponds to detection of light at approximately700 nm and is used to normalize the other data channels, although otherchannels could also be used. From the tables 302, 304, selection of thedata channels 308, 310 correspond to light detected from emission of the610 nm and 630 nm LED's, respectively, increase the likelihood thatprobe off space can accurately be determined. For example, in the datachannels corresponding to the 610 nm and 630 nm LED's the probe offspace 302 and the probe on space 304 do not overlap with or otherwiseconflict with one another. This distinction can be graphicallyrepresented as shown in FIGS. 4-7. For example, FIG. 4 illustrates thedistance between valid probe on data or probe on space 402 versus validprobe off data or probe off space 404 for data channels corresponding tothe detection of light at 610 and 620 nm. FIG. 5 similarly illustratesthe space separation for data channels corresponding to the detection oflight at 610 and 630 nm, and FIG. 6 illustrates the space separation fordata channels corresponding to the detection of light at 620 and 630 nm.Reviewing FIGS. 4-6 collectively, FIG. 5 shows the clearest or largestdistinction between potentially valid probe on space 502 and probe offspace 504. Thus, were an oximeter system to made a two (2) dimensionalcomparison using the foregoing data channels, it would be best served touse the data channels corresponding to the detection of light at 610 and630 nm.

FIG. 7 illustrates a three (3) dimensional graph that combines the datachannels corresponding to the detection of light at 610, 620 and 630 nm.Although FIGS. 4 and 6 indicate that the data channel corresponding to620 nm is not ideal for the separation of spaces, the three (3)dimensional plot of FIG. 7 illustrates that higher dimensions of spaceincrease the separation between defined probe off 704 and probe on 702regions. Thus, in an oximeter having eight (8) wavelengths of emittedlight, a probe off and probe on space may be defined using as many asseven (7) dimensions (the eighth being used for normalization). Suchincreased dimensional analysis may advantageously provide everincreasing separation between defined probe off and probe on regions.

FIG. 8 illustrates a simplified exemplary block diagram of a probe offdetector 802, according to an embodiment of the disclosure. As shown inFIG. 8, the probe off detector 802 includes inputs of data channels 804corresponding to two (2) or more wavelengths of emitted light, probe offdata 806, and in some embodiments, probe on data 806. Comparison ofcharacteristics of the data channels, such as, for example, ratio data,can be compared to multidimensional probe off and/or probe on space todetermine and output 808 of a probe off indication.

FIG. 9 illustrates an exemplary probe off determination process 900,according to an embodiment of the disclosure. The process 900 includesblock 902 where probe off data is collected from, for example, clinicaltrials, mathematical models, extrapolated data, non-probe on data, orthe like. In block 904, the collected probe off (and, in someembodiments, probe on data) may be reviewed to determine characteristicsthat reduce crossover between probe off and probe on space. For example,characteristics may be chosen that decouple the probe off determinationsfrom measurement determinations. For example, when the characteristicscomprise ratio data, or normalized data channels responsive to intensitydata channels from the sensor, the ratio data corresponding toparticular wavelengths may indicate a greater separation between validparameter data (probe on conditions) and probe off conditions. In someembodiments, increasing the dimensions may advantageously cause furtherseparation between valid and invalid conditions.

In block 906, the probe off data (and in some embodiments, probe ondata) is stored in memory on a patient monitor. In an embodiment, suchprobe on or off data may be updated through upgrading tools, networkconnectivity such as the internet, smartcards, or other memory devicesor network computing. In block 908, the patient monitor acquires datafrom a measurement site. The acquisition may be at or near a start ofdata acquisition, periodically throughout acquisition, randomly, inresponse to particular conditions or changes in conditions, combinationsof the same or the like. In block 910, the DSP compares characteristicsof the acquired data to the characteristics stored as probe on and offdata. Block 912 determines whether a probe off exists by determiningwhether the characteristics fall within one of the probe off or probe onspaces. When the acquired data falls within the probe off space, a probeoff condition is determined to exist and in block 914, the DSP triggersa probe off indicator. The probe off indicator may be an audible sound,such as a constant or varying tone or beep, a visual indicator, such asa flashing and/or colored display or display element(s), combinations ofthe same or the like. The probe off indicator may comprise help screensor training indicia to guide a caregiver on how to properly attach theprobe. The probe off indicator may continue to activate until the probeis properly positioned. In the case of a probe off condition, theprocess 900 returns to block 908 and acquires data from the measurementsite. When a probe off condition does not exist at block 912, block 914determines parameter measurements according to probe on operation of thepatient monitor.

While the probe off indicator has been described in certain embodimentsherein, other embodiments of the present disclosure will be known tothose of skill in the art from the descriptions herein. Moreover, thedescribed embodiments have been presented by way of example only, andare not intended to limit the scope of the disclosure. Moreover, thoseof skill in the art understand that information and signals can berepresented using a variety of different technologies and techniques.For example, data, instructions, commands, information, signals, bits,symbols, and chips that can be referenced throughout the abovedescription may be represented by voltages, currents, electromagneticwaves, magnetic fields or particles, optical fields or particles, or anycombination thereof.

Those of skill in the art further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein can beimplemented as electronic hardware, computer software, or combinationsof both. To illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans can implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein can be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor can be a microprocessor, but in thealternative, the processor can be any conventional processor,controller, microcontroller, or state machine. A processor can also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein can be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module can reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or other form of storage medium known in the art. A storagemedium is coupled to the processor, such that the processor can readinformation from, and write information to, the storage medium. In thealternative, the storage medium can be integral to the processor. Theprocessor and the storage medium can reside in an ASIC. The ASIC canreside in a user terminal, physiological monitor and/or sensor. Theprocessor and the storage medium can reside as discrete components in auser terminal, physiological monitor and/or sensor.

Although the foregoing disclosure has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art from the disclosure herein. Additionally,other combinations, omissions, substitutions and modifications will beapparent to the skilled artisan in view of the disclosure herein.Moreover, it is contemplated that various aspects and features of thedisclosure described can be practiced separately, combined together, orsubstituted for one another, and that a variety of combination andsubcombinations of the features and aspects can be made and still fallwithin the scope of the disclosure. Furthermore, the systems describedabove need not include all of the modules and functions described in thepreferred embodiments. Accordingly, the present disclosure is notintended to be limited by the recitation of the preferred embodiments,but is to be defined by reference to the appended claims.

Additionally, all publications, patents, and patent applicationsmentioned in this specification are herein incorporated by reference tothe same extent as if each individual publication, patent, or patentapplication was specifically and individually indicated to beincorporated by reference.

1. A method of determining whether an optical probe in an oximetrysystem is improperly positioned, the method comprising: acquiring dataresponsive to light attenuated by body tissue; comparing characteristicsof said data to a probe off space, wherein at least a portion of saidprobe off space comprises data acquired during known probe offconditions; and when said characteristics fall within said probe offspace, outputting a probe off indication capable of alerting a caregiverto an improperly positioned probe condition, wherein said characteristiccomprises normalized data channels corresponding to at least two emittedwavelengths of light, and wherein said at least two emitted wavelengthsof light are selected to reduce a likelihood of overlap between saidprobe off space and probe on space.
 2. The method of claim 1, whereinsaid at least two wavelengths comprise approximately 610 nm andapproximately 630 nm.
 3. The method of claim 1, comprising comparingcharacteristics of said data to a probe on space, wherein at least aportion of said probe on space comprises data acquired during knownprobe on conditions; and when said characteristics fall within saidprobe on space, determining measurements of monitored physiologicalparameters.
 4. A patient monitor comprising: an input receiving dataresponsive to light attenuated by body tissue, wherein the lightcomprises light emitted at least two of emission centroids ranging fromabout 605 nm to about 614 nm, from about 615 nm to about 624 nm, fromabout 625 nm to about 635 nm, from about 655 nm to about 665 nm, fromabout 690 nm to about 710 nm, from about 720 nm to about 740 nm, fromabout 785 nm to about 825 nm, and from 875 nm to about 935 nm; a memorystoring probe off data corresponding to probe off space, wherein atleast some of said probe off space corresponds to data acquired duringknown probe off conditions; and a processor programmed to compare saiddata received at said input with the probe off data to determine anoccurrence of a probe off condition, wherein said comparing includescomparing normalized data channels responsive to said data received atsaid input, said normalized data channels selected to reduce alikelihood of overlap between said probe off space and probe on space,said processor also programmed to output a probe off indication upondetermination of said occurrence.
 5. The patient monitor of claim 4,wherein said centroids comprise at least two or more of centroids atabout 610, about 620, about 630, about 660, about 700, about 730, about800 or about 905 nm.
 6. The patient monitor of claim 4, wherein saidprobe off space comprises a multi-dimensional probe off space.
 7. Thepatient monitor of claim 6, wherein said multi-dimensional probe offspace includes data responsive to wavelengths of approximately 610 nmand approximately 630 nm.
 8. The patient monitor of claim 6, whereinsaid multi-dimensional probe off space includes data responsive towavelengths of approximately 610 nm, approximately 620 nm andapproximately 630 nm.
 9. The patient monitor of claim 4, wherein thememory stores probe on data corresponding to said probe on space,wherein at least some of said probe on space corresponds to dataacquired during known probe on conditions; and wherein said processor isprogrammed to compare incoming data with the probe on data to determinesaid occurrence of said probe off condition.
 10. A patient monitorconfigured to received signals from a noninvasive optical sensoroperatively attached to a patient, to process said signals and determinemeasurement values for one or more physiological parameters, and tooutput display indicia responsive to said measurement values to one ormore displays, said monitor comprising: a sensor interface configured toreceive said signals from said noninvasive optical sensor, said signalsbeing responsive to light attenuated by tissue of said patient; aprocessor configured to process said signals to determine a plurality ofdata channels, each data channel responsive to portions of said signalsthat represent absorption of a different wavelength of light, saidprocessor also configured to normalize said data channels and to selectat least two of said normalized data channels to compare topredetermined data representing a probe off space and a probe on space,said at least two data channels selected to reduce a likelihood ofoverlap between said data of said probe off space and data of said probeon space, said processor outputting a probe off signal when one or moreof said selected data channels sufficiently match said data representingsaid probe off space; and a caregiver alert configured to activate uponsaid outputting of said probe off signal to convey to a caregiver thatsaid noninvasive optical sensor is not properly aligned with said tissueof said patient.
 11. The patient monitor of claim 10, wherein said atleast two normalized data channels are each responsive to absorption bya different one of at least two of wavelengths of light ranging fromabout 605 nm to about 614 nm, from about 615 nm to about 624 nm, or fromabout 625 nm to about 635 nm.
 12. The patient monitor of claim 11,wherein said wavelengths of light include at least two of about 610 nm,about 620 nm or about 630 nm.